Complexity_ A Guided Tour - Melanie Mitchell [101]
In spite of this prediction, there are notable counterexamples to selfishness at all levels of the biological and social realms. Starting from the bottom, sometime in evolutionary history, groups of single-celled organisms cooperated in order to form more complex multicelled organisms. At some point later, social communities such as ant colonies evolved, in which the vast majority of ants not only work for the benefit of the whole colony, but also abnegate their ability to reproduce, allowing the queen ant to be the only source of offspring. Much later, more complex societies emerged in primate populations, involving communal solidarity against outsiders, complicated trading, and eventually human nations, governments, laws, and international treaties.
Biologists, sociologists, economists, and political scientists alike have faced the question of how such cooperation can arise among fundamentally selfish individuals. This is not only a question of science, but also of policy: e.g., is it possible to engender conditions that will allow cooperation to arise and persist among different nations in order to deal with international concerns such as the spread of nuclear weapons, the AIDS epidemic, and global warming?
FIGURE 14.2. Alice and Bob face a “Prisoner’s Dilemma.” (Drawing by David Moser.)
THE PRISONER’S DILEMMA
In the 1950s, at the height of the Cold War, many people were thinking about how to foster cooperation between enemy nations so as to prevent a nuclear war. Around 1950, two mathematical game theorists, Merrill Flood and Melvin Drescher, invented the Prisoner’s Dilemma as a tool for investigating such cooperation dilemmas.
The Prisoner’s Dilemma is often framed as follows. Two individuals (call them Alice and Bob) are arrested for committing a crime together and are put into separate rooms to be interrogated by police officers (figure 14.2). Alice and Bob are each separately offered the same deal in return for testifying against the other. If Alice agrees to testify against Bob, then she will go free and Bob will receive a sentence of life in prison. However, if Alice refuses to testify but Bob agrees to testify, he will go free and she will receive the life sentence. If they both testify against the other, they each will go to prison, but for a reduced sentence of ten years. Both Alice and Bob know that if neither testifies against the other they can be convicted only on a lesser charge for which they will go to jail for five years. The police demand a decision from each of them on the spot, and of course don’t allow any communication between them.
If you were Alice, what would you do?
You might reason it out this way: Bob is either going to testify against you or keep quiet, and you don’t know which. Suppose he plans to testify against you. Then you would come out best by testifying against him (ten years vs. life in prison). Now suppose he plans to keep quiet. Again your best choice is to testify (go free vs. five years in prison). Thus, regardless of what Bob does, your best bet for saving your own skin is to agree to testify.
The problem is that Bob is following the exact same line of reasoning. So the result is, you both agree to testify against the other, giving each of you a worse outcome than if you had both kept quiet.
Let me tell this story in a slightly different context. Imagine you are the U.S. president. You are considering a proposal to build a powerful nuclear weapon, much more powerful than any that you currently have in your stockpile. You suspect, but don’t know for sure, that the Russian government is considering the same thing.
Look into the future and suppose the Russians indeed end up building